Certain fatty acid methyl esters originating from vegetable oils, animal fats, and oil-seeds are known as biodiesel. Biodiesel fuel has received considerable attention in recent years, as it is a biodegradable, renewable and non-toxic fuel. It contributes no net carbon dioxide or sulfur to the atmosphere and emits less gaseous pollutants than normal diesel (Lang, et. al. 2001. Bioresour. Technol. 80:52-62; Antolin, et. al. 2002. Bioresour. Technol. 83:111-114; Vicente, et. al. 2004. Bioresour. Technol. 92:297-305). Biodiesel, primarily rapeseed methyl ester, has been in commercial use as an alternative fuel since 1988 in many European countries (Lang, et. al. 2001. supra). In spite of the favorable impact that its commercialization could provide, the economic aspect of biodiesel production prevents its development and large-scale use, mainly due to the high cost of vegetable oil (Antolin, et. al. 2002; Lang, et. al. 2001, supra). The cost of biodiesel is significantly higher than that of fossil-fuel-based diesel (Zhang, et. al. 2003. Bioresour. Technol. 89:1-16), thus, methods and compositions that reduce the high cost of biodiesel production is being undertaken, such as the exploration of methods that involve minimizing raw material costs.
The research of liquid fuel produced from microalgae began in the mid-1980's. Typically, the microalgal oil was extracted using process steps applied to dried microalgal biomass. The cells were freeze-dried, ruptured, and subjected to extraction and purification using a two or three-step process involving organic solvents and vacuum distillation. The recovered and purified oil was then transesterified in the presence of an alcohol and an appropriate catalyst (Narasimiharao, K., Lee, A., Wilson, K. 2007. “Catalysts in Production of Biodiesel: A review.” Journal of Biobased Materials and Bioenergy. 1 (1):19-30; Demirbas, A. 2009. “Progress and recent trends in biodiesel fuels.” Energy Conversion and Management. 50:14-34) to create the fatty acid methyl (or ethyl) esters that were then either evaluated by gas chromatography (GC) analysis or used as biodiesel fuel. Modifications to these methods were soon proposed, however, although these modified approaches improved recovery yields and decreased the time for GC analysis of cellular lipids, they did not diminish the voluminous use of a flammable alcohol nor diminish the need for an organic solvent (e.g., hexane) for final purification if higher chain alcohols are used in the process. For these and other reasons, large scale commercial application of direct transesterification remains limited.
Accordingly, embodiments of the invention disclosed herein relate to methods and compositions for carrying out energetically feasible methods for solvent-based extraction, recovery and/or production of bio-oil or fatty acid ester product from a variety of biomass starting materials.